R
1
conductor AC resistance [Ω/km]
W
658
ρ
earth
n
f
the equivalent depth [m] of the earth return path
ρ
earth
earth resistivity [Ωm]
r
en
r
a
a
a
⋅
⋅
⋅
12
2
23
2
31
2
3
3
the equivalent radius [m] for conductor bundle
r
radius [m] for single conductor
a
xy
distance [m] between phases x and y
Ph leakage Ris and Ph capacitive React settings
The
Ph leakage Ris and Ph capacitive React settings are used for improving fault
distance estimation accuracy for earth faults. They are critical for an accurate fault
location in unearthed networks. In other types of networks they are less critical.
The
Ph leakage Ris setting represents the leakage losses of the protected feeder
in terms of resistance per phase. The
Ph capacitive React setting represents the
total phase-to-earth capacitive reactance of the protected feeder per phase. Based
on experience, a proper estimate for
Ph leakage Ris should be about 20…40 × Ph
capacitive React.
Figure 450: Equivalent diagram of the protected feeder. R L0F = Ph leakage Ris.
The determination of the
Ph capacitive React setting can be based either on
network data or measurement.
If the total phase-to-earth capacitance (including all branches) per phase C
0F
of the
protected feeder is known, the setting value can be calculated.
Ph capacitive React
C
n
F
=
⋅
(
)
1
0
ω
(Equation 170)
Protection related functions
1MRS757644 H
848
620 series
Technical Manual
